In a die bonding apparatus a silicon wafer is supported on a carrier such as a wafer table. The wafer is generally circular and is made up of a large number of electronic components or dice which are arranged in a matrix. The dice are picked up from the wafer table by a pick-and-place device which transfers the dice individually from the wafer to bonding positions comprising respective bond pads on a substrate such as a leadframe.
Conventionally, the dice are picked up from a fixed pick-up position and then transferred to a bonding position on a substrate. The wafer is supported on a movable wafer table which re-positions the wafer so that each die may be picked up by the pick-and-place device from the pick-up position. The wafer table is adapted to move the wafer in mutually orthogonal X and Y directions, and to achieve maximum speed, the wafer table is adapted to move in both the X and Y directions simultaneously. In this way any die on the wafer can be moved to the pick-up position for die pick-up. Such conventional designs have disadvantages with the introduction of larger wafers that are becoming more common in the field.
One factor affecting throughput is the travel distance of the pick-and-place device between the pick-up position and the bonding position, and throughput is generally affected by the size of the wafer. For example, to move a die on a 6-inch diameter wafer to the pick-up position, the wafer table must have a range of travel of at least 6 inches in both the X and Y directions. This distance increases with larger wafers so that more time is required to transfer dice from a larger wafer to substrates for bonding. Therefore, throughput is reduced when the wafers are larger. The footprint of the wafer table must also be increased to provide sufficient space for the translational displacement of the wafers which is dependent on the locus of its working area. As a result, the die bonding apparatus is also larger.
FIG. 1 illustrates a conventional die bonding apparatus with a conventional die transfer system 100. A wafer table supporting a wafer 101 with singulated dice 102 is movable along X and Y directions to move each die 102 to a fixed die pick-up position 108. A die transfer device 104 includes a die pick tool 106 to pick up a die 102 from a die pick-up point 108 to a bonding point 110 on a substrate 112. The substrate 112 is indexed along a substrate holder 114 to position respective bond pads to the bonding point 110 to receive the dice 102. Each die 102 is moved to the die pick-up point 108 by moving the wafer 101 within a locus 116 or working area in order to move each die 102 on a wafer 101 of diameter D. The minimum travel distance of the die pick tool 106 from the die pick-up point 108 to the side of the substrate holder 114 closest to the wafer table is at least greater than D and the working envelope or area required for movement by the wafer table is 2D.